The present invention relates in general to a gumming roll apparatus for applying gum to blanks and pertains, more particularly, to an apparatus for applying gum to envelopes during continuous processing and operation of a gumming machine. The roller combination of this invention is an improvement over the conventional low speed gumming station roller combination.
With the conventional gumming roll apparatus a gumming station is typically one of a number of stations in an envelope processing apparatus or other continuous processing apparatus. For example, it is common to provide a gumming station in a conventional envelope making machine or in apparatus intended to apply gum (e.g., a self-sealing latex adhesive) to envelopes already formed and processed solely for the purpose of applying a desired adhesive.
Self-sealing envelopes typically require cooperating adhesive deposits applied to both a flap and an enclosure portion of an envelope. The envelope is gummed in order that a sealed envelope will be formed when the adhesive carrying portions are pressed together. It will be understood that other articles, forms, or enclosures may be processed in an equivalent manner.
The conventional gumming stations typically satisfy the operational requirements with a combination gum box, roller for transferring the gum or adhesive to one or more gummer pads on a gummer roll. The conventional apparatus includes the gum box or trough for supplying the adhesive of choice, one or more intermediate transfer rollers for transferring the adhesive to the adhesive application roller.
These conventional roller arrangements provide for the physical transfer of the adhesive as rotation of the roller carries the roller surface through the gum box and the adhesive which agitates the adhesive. Typical adhesives, particularly latex adhesives, foam or froth as a consequence of agitation.
It is a known drawback of gumming apparatus that the foam or froth may be transferred on the rollers to the envelope or other adhesive receiving portion of an article processed at the gumming station. The foam or froth creates a blemish on the adhesive which may not provide a desired adherence. It is typical to reject items with this foam or froth blemish. As a result, conventional gumming stations and apparatus have a drawback of a limited speed of operation.
The gumming station speed limitation creates an overall equipment limitation since the transfer roller must operate at a speed sufficient to transfer adhesive to the gumming roller and the latter roller rotates in a manner to provide registration between gummer pads and items passing through the gumming station.
Reducing the rotational speed of a gumming roller without reducing the processing speed or output of the gumming station would require a relatively large gumming roller circumference with a limited rotational speed in conventional apparatus. This solution has numerous drawbacks, including space limitation since the gummer station is often one of a number of stations. Another drawback associated with a larger and slower gumming roller is that the adhesive could dry out between applications of fresh adhesive from the transfer roller.
Accordingly, it is an object of the present invention to provide an improved gum roll apparatus that is adapted to increase the processing speed of a gumming station. With the roller arrangement of this invention the gumming station output of either a stand alone station or a gumming station incorporated into a larger apparatus will be increased without significant adhesive degradation due to foam or froth transferred to a workpiece from the gumming roller.
Another object of the present invention is to provide an improved gum roll apparatus that is constructed to provide a more uniform adhesive transfer with an increase in gum roller rotational speed and thus provide an increased output for an apparatus incorporating the arrangement of this invention.
A further object of the present invention is to provide an improved gum roll apparatus that is adapted for use with existing equipment. The improved roller combination of this invention may be incorporated into existing equipment with only minor timing modifications to ensure that the adhesive is applied in desired registration with the envelope flap, or the like.
Still another object of the present invention is to provide an improved gum roll apparatus that may be readily adapted for use in a gumming machine for applying adhesive to envelope flaps.
Still a further object of the present invention is to provide an improved gum roll apparatus that allows an increase in gummer cylinder rotational speed without a corresponding increase in adhesive foaming. The combination of this invention substantially eliminates adhesive or gum foaming on the gummer cylinder and associated gummer pads.